While Farkas in The Art of French Horn Playing does address the topic of etude study in the section on practice, he did not address the topics of what solo and orchestral works are the most important to study. This is a story that is repeated in most of the classic horn methods written since Farkas.
A few suggestions
As this is an information gap on a topic of interest to many horn players, I have had on my Horn Articles Online site for a number of years now two lists, described below.
Horn Solo and Chamber Works–Essential solo and chamber music literature that all students of the horn should know, study, and own recordings of.
Orchestral Excerpts—An organized list of the works most requested at auditions for orchestral performing positions in the United States.
Both of these articles are based on surveys I did several years ago. The first, of solos, was somewhat more informal but based on a combination of books and recordings and articles, to determine which works were in fact most frequently performed. The orchestral excerpt list is based on a more formal survey of audition lists and was published as “A New ICSOM Audition List Survey” in the October, 2002 issue of The Horn Call.
See also this list for a more focused list of solos and excerpts–Horn Study Lists
A few “standard” solos to know
To offer a bit more detail to close, my “top 18” list of horn solos is the following. I will freely admit that it is a list a bit heavily skewed to standards but that was the nature of the survey results. Anyone versed in the horn repertoire could come up with their own top ten lists, but I believe most of those lists would include mostly works drawn from this list.
• Beethoven: Sonata, Op. 17
• Brahms: Trio, Op. 40 for Horn, Violin, and Piano
• Britten: Serenade, Op. 31 for Tenor, Horn, and Strings
• Dukas: Villanelle
• Haydn, J.: Concerto No. 1 in D; Concerto No. 2 in D
• Hindemith: Sonata for Horn
• Mozart: Concerto No. 1 in D, K. 412; Concerto No. 2 in E-flat, K. 417; Concerto No. 3 in E-flat, K 447; Concerto No. 4 in E-flat, K. 495; Concert Rondo; Quintet for horn and strings, K. 407
• Schumann: Adagio and Allegro, Op. 70; Konzertstuck for four horns and orchestra
• Strauss, R.: Concerto No. 1, Op. 11; Concerto No. 2
• Telemann: Concerto in D